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Old 09-01-2011, 12:30 PM   #1
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Question Electrical Weirdness

Hi, All

By fixing what turned out to be a bad ground connection, I've made this weird phenomenon go away.
BUT
I'd sure be interested in knowing HOW it was even possible for it to occur!
First I'll explain that I have a very small trailer with very simple wiring. The only interior electrics are lights, the converter, and the fridge(when switched).
Other than a common ground, there is no connection between the traveling lights/brakes and the interior trailer electrics.

I was drycamping (no shorepower) a few weeks ago, and the first night I was unhitched I turned an interior light on and nothing happened- at least inside the trailer.
(The converter switch was in the correct position, by the way.)
I happened to notice a slight "glow" outside and discovered that I had turned the running lights on at all four corners of the trailer!
Interior switch on= running lights on.
And I got the same result from each of the interior switches in the trailer.
Crazy, right?
But that's not the weirdest part.

When the running lights came on......

THE TAILLIGHTS STAYED OFF!

And they're on the exact same wire.

Can anybody tell me how on earth that's possible????
In layman's terms, please- I'm pretty thick when it comes to electrical stuff.

Thanks, I hope!

Francesca
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Old 09-01-2011, 12:52 PM   #2
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Current paths

Without actually touching your trailer I can only guess, and it can be very complicated, but I will tr to make it simple.

Eaxh device must have power, and for the power it requires a path, and the path is usually 2 wires, HOT and RETURN.

In automotive/RV most devices only have a single wire for HOT, the return is a metal to metal connection to the chassis which is called ground.

When you have a wood structure then there are 2 wires, and the return or ground connections are usually tied together and connected the the chassis here and there.

What happens is one of these may come loose from the chassis, loosing the ground, but all of the devices connected together at that point are still connected together, so now instead of a bunch of things in parallel, they are in series.

A voltmeter across the device will indicate 12 volts, good, or who knows what depending in the resistance of the devices.
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Old 09-01-2011, 01:01 PM   #3
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Thanks-
That much I think I get!

My question is- why would ONLY the running lights come on, and not the taillights?
They're all on the same wire!

Francesca
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Old 09-01-2011, 01:39 PM   #4
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Actually it may be the same bulb but it has 2 filiments inside it. One for brakes one for running lights. Some manufacturers use a single filiment for both brake and turn signal but that's a different circuit then running lights. Your trailer lit the filimentsin the running lights looking for a path to ground. When you fixed the -12 volt wire on the battery you also fixed the return path for the interior lights to ground. Ground and -12 volts are tied together at the trailer frame.
-Paul R. Haller-
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Old 09-01-2011, 02:45 PM   #5
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I really appreciate your patience, guys!
It's really only my own curiosity now, since I did solve the problem...
But this really mystifies me.
And I think I'm being unclear about the lingering question...
Click image for larger version

Name:	Trillium wiring diagram0001.jpg
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Here's the wiring diagram for the trailer.
(note: scanner didn't pick up white/ground, but it's there!)
The green wire is tails AND running lights.
(click to see colors better)
As you can see, that's all one wire/series.

What I just don't get is why the markers lit up and the tails didn't!

Why would that transient power bypass the taillights???

Thanks again

Francesca AKA "Curious George"
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Old 09-01-2011, 03:40 PM   #6
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Well,maybe if the running lights filiments have a lower resistance then the taillight filiments it could make the running lights glow dimly while the rear lights very, very dim or not at all.
-Paul R. Haller-
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Old 09-01-2011, 03:56 PM   #7
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Hi, Paul

You know, it just occurred to me when I read your post that the running lights are (my retrofit) LED's and the taillights are the old filament bulb type.
Does that dovetail with your explanation?
Could/would the LED's have lower resistance?

Thanks!

Francesca
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Old 09-01-2011, 04:01 PM   #8
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Paul that was very good remote diagnosis. Even without all the details you nailed it!
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Old 09-01-2011, 04:33 PM   #9
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So the LED's are the path of least resistance!
I'm getting it!
This is so great...
I won't bore you all with the torturous details of my electrical adventures while
Alone in the Wilds of California .
But I will say that those days combined with your help just now have taught me more about electricity than I ever thought I could learn.
Thanks so much!
Just one more thing, if I may ask it-
Did that same principle of physics cause the initial strangeness when I turned on the inside light, only to see the markers come on?
Did I energize the badly grounded circuit, causing it to seek ground and find it- or bleed out or whatever- back along the groundwire to the "point of least resistance" at the markers?


Francesca
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Old 09-01-2011, 08:04 PM   #10
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Hi Francesca, The bad ground caused all your troubles. Think of electricity as water flowing through a pipe. The only difference is that electricity has to get back to its point of origin. If you need more volume of water you need a bigger pipe. This is analogous to amps in electricity. More amps = bigger wire.

The pressure in a pipe pushing the water is equal to the volts pushing the amps through wire. Resistance is literally a device that reduces flow like a kink in a hose and is measured in Ohms resistance.

With a bad ground the electricity is looking to get back home to the battery any way it can. It will always choose the path of least resistance. Your LED light draws almost no current or amps. The Filiment in the tail lights gives off way more heat then light and as a result more amps and more resistance to flow. When turning on the light in the trailer the current followed Ohms law and followed the path of least resistance through the LED but not the tailights. Incedently, that's why incandescent light is being phased out in favor of compact flourescent lights or better yet LED. Incandescents draw more power then CFL or LED because they produce heat and light is just a byproduct. LEDs conversely give off almost no heat and that's why they are way more energy efficient and the same is true to a degree for CFLs.

If you are still interested and haven't yet fallen asleep... look up Ohms law. Where V= volts , I = amps and R = resistance. This law defines the relationship between resistance, current or amps, and voltage. You will learn a lot.
Anyway, I'm glad your lights are working and the problems are solved.
-Paul R. Haller-
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Old 09-01-2011, 08:31 PM   #11
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Hi, Paul

The clarity of your explanation can only be described as brilliant.
If you're not a professional teacher, you should be.
And I will look up Ohms's Law- thanks to you, I think understanding it is actually within my reach!

Here's an apple for my Teacher:




........Francesca
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